Types of Lamps (Bulbs) used for Street Lighting

Tungsten Filament Lamps

The Incandescent Lamp or Tungsten Filament Light Bulb produces light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process that returns metal to the filament prevents its evaporation. The light bulb is supplied with electrical current by feed-through terminals or wires embedded in the glass. Most bulbs are used in a Lamp Holder (a housing giving mechanical support to the bulb, keeping its terminals in contact with the supply current terminals).

Incandescent bulbs are produced in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment (Control Gear), and have a low manufacturing cost and work equally well on either alternating current or direct current. As a result, the incandescent lamp is widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting.

The initial cost of an incandescent bulb is small compared to the cost of the energy it uses over its lifetime. A comparison of incandescent lamp operating cost with other light sources must consider the luminous efficacy produced by each lamp. The comparison must include illumination requirements, capital cost of the lamp, labour cost to replace lamps, various depreciation factors for light output as the lamp ages, effect of lamp operation on heating and air conditioning systems, and energy consumption as well.

Liverpool's Side Roads and some Main Roads used Tungsten Filament Lamps as standard, only selected roads had converted to sodium during and after the second world war, a lot were strung from the wires used to supply power to the tramways, gradually the Tungsten Filament Lamps on all main roads were replaced with Mercury Vapour and later Low Pressure Sodium, Lighting.

Mercury Vapour Lamps

Modern Iwasaki EYE Clear 80 watt Mercury Vapour Lamp

The Mercury Vapour Lamp is a Discharge Lamp made in sizes from 40 watts to 2000 watts they consist of a Discharge Tube (Arc Tube) which contains Argon Gas and Mercury in a excited state to produce Light, the Arc tube was made of Glass later Quartz and is enclosed within a Soft Glass or Hard Borosilicate Bulb, the Outer Bulb may be Clear, Pearl or Coated with a Fluorescent Phosphor, and may be Elliptical, and in cases on Early Lamps, Tubular or Pear Shape, in either case the Outer Bulb provides Thermal Insulation, Protection from Harmful Ultra Violet Radiation and convenient, Mounting for the Arc Tube.

The Mercury Vapour lamps are often used because they are relatively efficient. Phosphor Coated Bulbs offer better Colour Rendering Index than either High or Low Pressure Sodium Vapour Lamps. Mercury Vapour lamps also offer a very long lifetime, as well as intense lighting for several special purpose applications.

The Mercury Vapour lamp is a Discharge Lamp, and requires a Ballast to prevent it from taking excessive current. The auxiliary components are substantially similar to the Ballasts used with Fluorescent Lights. In fact, the first British 80 watt Fluorescent Tubes were designed to operate from 80-watt mercury Vapour Ballasts.

The Metal Halide Lamp is a Discharge Lamp made in sizes from a mere 20 watts to a colossal 3500 watts they consist of a Discharge Tube made from either Quartz or Ceramic (Arc Tube) which contains Mixture of Argon Gas and Bromine, Iodine and Sodium, which is at a Higher Pressure, compared to the Mercury Lamp, and depending on the Additives, in a excited state to produce Warm White to Daylight Light, (some Lamps are designed to emit Coloured Light for Architectural Floodlighting), the Arc tube is enclosed within Clear, Coated Bulb, the Outer Bulbs are either Elliptical, Tubular, Linear, or Reflector, in either case the Outer Bulb provides Thermal Insulation, and for Supporting for the Arc Tube

The Metal Halide Lamps are often used because they are very efficient. although the Colour Rendering is Excellent, a lot better than Mercury Lamps, they are Ideal for Long Burning Hours as well as Emitting Excellent Colour Retention Light, they are Ideal Light Sources for City Streets and Residential Roads where Better Coloured Light is required, and where CCTV is in use.

The Metal Halide Lamp is a Discharge Lamp, and requires a Ballast to prevent it from taking excessive current. The Ballast is a Simple Choke type Ballast, similar to the Mercury Lamp Ballast, but most require a Electronic Ignitor which produces a high Voltage Kick of 2300 to 5000 volts which strikes the arc, then the ballast them runs the lamp at the desired current, the Metal Halide Lamps are designed to replace Mercury Lamps in existing Light using Existing Mercury Ballast and Electronic Ignitor, and Other Metal Halide Lamps are designed to be used on SON High Pressure Sodium Gear, others have Internal Starters which simplifies the wiring and they do not require a Electronic Ignitor.

Modern Metal Halide Lamps such as the CDM-TP MW, and Cosmowhite Metal Halide Lamps are High Performance Lamps and can only be operated on Specific Electronic Ballasts Only. whilst the CMH CDM and CDO Ceramic Metal Halide Lamps can be operated on Both Existing Magnetic Ballasts and Ignitor as well as Electronic Ballasts, and are available from 50 watts to 400 watts, which makes them Ideal for converting Yellow High Pressure Sodium Lighting to White Light in all types of street Lighting Applications whether it is from a Residential Street or Cycle Path to a Major Traffic Route such as a Motorway etc..

Sodium Vapour Lamps

Since its commercial introduction in 1932, the Low Pressure Sodium lamp has consistently maintained its enviable position as the most efficient light source available Present-style Low Pressure Sodium lamps are known as the SOX type, and the entire global supply of approximately four million SOX Lamps per Year are made exclusively in the UK by OSRAM and Philips at Hamilton, UK. A ancillary factory in India used to assemble lamps from British made discharge Tubes until recently. Despite increasing competition from High Pressure Sodium Lamps (See Below) and Metal Halide Lamps, the market for this Light source remains quite stable and continues commercial introduction in 1932, the Low Pressure Sodium lamp has consistently maintained its enviable position as the most efficient light source available Present-style Low Pressure Sodium lamps are known as the SOX type, and the entire global supply of approximately four million SOX Lamps per Year are made exclusively in the UK by OSRAM and Philips at Hamilton, UK. A ancillary factory in India used to assemble lamps from British made discharge Tubes until recently. Despite increasing competition from High Pressure Sodium Lamps (See Below) and Metal Halide Lamps, the market for this Light source remains quite stable and continues to be specified for new installations.

The Low Pressure Sodium Lamp (Type SOX)

Philips 35 watt SOX-PSG Low Pressure Sodium Lamp

The Low Pressure Sodium Vapour Lamp is a Discharge Lamp first used for Street Lighting in the early 1930's (Type SO/H). and is made in sizes from 10 watts to 180 watts they consist of a Discharge Tube Bent into a Tight U Shape (Arc Tube) which contains Mixture of Neon/Argon Gas and Sodium, which in a excited state to produce Yellow Light, the Arc Tube was made of Sodium Resistant Glass and is enclosed within a Infra-Red Film Coated Bulb, the Outer Bulb looks Clear, but with a Greenish/pink look, in either case the Outer Bulb provides Thermal Insulation, and for Supporting for the Arc Tube,

The SOX Sodium Vapour lamps are often used because they are very efficient. although the Colour Rendering is Poor and these Lamps emit Yellow Light, they are Ideal for Long Burning Hours as well as Emitting Light in Poor Weather.

The Sodium Vapour Lamp is a Discharge Lamp, and requires a Ballast to prevent it from taking excessive current. The Ballast is a Special Auto Transformer type which first produces a high Voltage Kick of 600 volts which strikes the Arc Tube, then the ballast them runs the lamp at the desired current, Later Gear use a Simple Choke Type Ballast and a 2 Wire Parallel Ignitor connected across the Lamp which emits a 1000 to 1500 Volt kick to strike the Arc Tube.

The High Pressure Sodium Vapour Lamp is a Discharge Lamp made in sizes from 35 watts to 1000 watts they consist of a Discharge Tube made from Sintered Alumina Oxide (Arc Tube) which contains Mixture of Neon/Argon Gas and Sodium, which is at a Higher Pressure, compared to the SOX Lamp, in a excited state to produce Golden Yellow Light, the Arc tube was made of Sintered Alumina Oxide Material and is enclosed within Clear, Coated Bulb, the Outer Bulbs are either Elliptical, Tubular Linear, or Reflector, in either case the Outer Bulb provides Thermal Insulation, and for Supporting for the Arc Tube.

The SON Sodium Vapour lamps are often used because they are very efficient. although the Colour Rendering is Poor but better than SOX, and these Lamps emit Golden Yellow Light, they are Ideal for Long Burning Hours as well as Emitting better Colour Retention Light, they are Ideal Light Sources for City Streets and Residential Roads where Better Coloured Light is required.

The SON type Sodium Vapour Lamp is a Discharge Lamp, and requires a Ballast to prevent it from taking excessive current. The Ballast is a Simple Choke type Ballast, similar to the Mercury Lamp Ballast, but most require a Electronic Ignitor which produces a high Voltage Kick of 2300 to 5000 volts which strikes the arc, then the ballast them runs the lamp at the desired current, other SON Lamps are designed to replace Mercury Lamps in existing Light using Existing Mercury Gear, and Other SON Lamps have Internal Starters which simplifies the wiring and they do not require a Electronic Ignitor.

Light Emitting Diodes or LED's

Although Not a Electric Lamp or Light Bulb itself, but is classed as a Light Source, the LED or Light Emitting Diode has been increasingly used for street lighting applications, since around the 1990’s Light Emitting Diodes have become extremely Bright as well as available in different White Light Sources, from warm White to Cool Daylight White Light, also with Chip On Board (COB) Modules the Light Emitting Diode or LED has vastly becoming popular for Street Lighting, also with EU Regulations, Bans affecting Mercury, Standard SON and Standard Metal Halide Lamps, and the increasing Electricity Prices, Councils are adopting LED or Light Emitting Diodes for Street Lighting as well as Road Signs Bollards etc. LED Street lights can vary in Shape Size Design and Wattage, depending on the application from 10 watts for Cycle Paths etc. right up to 314 watts for High Mast Lighting, some Lights use a Single COB (Chip On Board) Light Emitting Diode others use a multiple array of LED’s within a Optical unit others are a Array of LED’s mounted as a Tube and are fitted with either a Normal ES or GES cap to use in existing SON/Mercury Street Light Fitting by simply By-passing the Control Gear.

Meanwell 30 watt COB (Chip On Board) LED Chip for Direct Fitting in to Street Lights

Goodlight 20 watt LED-360 SON Replacement Lamp for use in 70 watt SON Street Lights